Managing volumes in volume groups

ABSTRACT

Provided are a method, system, and program for managing volumes in volume groups configured in a storage system. A first set of volumes is assigned to a first volume group and a first host is assigned to the first volume group. A second set of volumes is assigned to a second volume group and a second host is assigned to the second volume group. The first host may only access volumes in the first volume group and the second host may only access volumes in the second volume group, wherein one volume is assigned to both the first and second volume groups to be accessible to both the first and second hosts.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method, system, and program formanaging volumes in volume groups.

2. Description of the Related Art

In certain computing environments, multiple host systems may communicatewith one or more control units, such as an IBM Enterprise Storage Server(ESS)®, for data in a storage device managed by the ESS receiving therequest. The control unit manages access to storage devices, such asinterconnected hard disk drives through one or more logical paths. (IBMand ESS are registered trademarks of IBM). The interconnected drives maybe configured as a Direct Access Storage Device (DASD), Redundant Arrayof Independent Disks (RAID), Just a Bunch of Disks (JBOD), etc. Thecontrol unit may configure logical volumes that define regions ofstorage space in the storage devices the control unit manages.

To allow one host to concurrently submit and have pending multipleInput/Output (I/O) requests toward one volume, the control unit mayassign alias addresses that point to a volume base address. The hostsmay then have multiple I/O requests pending to a volume by using thebase and alias addresses for that volume. The control unit may furtherassign both base volumes to a volume group and associate that volumegroup with one or more hosts, such that only hosts assigned to thevolume group may access volumes whose volume base addresses are assignedto the volume group. Further, a host may only access alias addressesthat point to volume base addresses assigned to the volume group towhich the host is assigned. Current systems may further restrict thebase volume to being in only one volume group.

SUMMARY

Provided are a method, system, and program for managing volumes involume groups configured in a storage system. A first set of volumes isassigned to a first volume group and a first host is assigned to thefirst volume group. A second set of volumes is assigned to a secondvolume group and a second host is assigned to the second volume group.The first host may only access volumes in the first volume group and thesecond host may only access volumes in the second volume group, whereinone volume is assigned to both the first and second volume groups to beaccessible to both the first and second hosts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of a computing environment.

FIG. 2 illustrates an embodiment of volume group information.

FIG. 3 illustrates an embodiment of alias address information.

FIGS. 4 and 5 illustrate an embodiment of operations to manage volumesin volume groups.

DETAILED DESCRIPTION

FIG. 1 illustrates an embodiment of a computing environment. Multiplehosts 2 a, 2 b . . . 2 n communicate Input/Output (I/O) requestsdirected to one or more storage systems 4 (only one is shown) to acontrol unit 6 over a network 8, where the control unit 6 manages accessto the storage system(s) 4. The control unit 6 includes a processor 10that executes I/O manager code 12 to configure and manage volumes 14 a,14 b . . . 14 n in the storage system(s) 4. A volume comprises a logicalrepresentation of a section of the storage space in the storage systems4 that may be referenced by the hosts 2 a, 2 b . . . 2 n. The controlunit 6 includes a memory 16, such as a non-volatile memory including anI/O cache 18 and information used to manage the configured volumes 14 a,14 b . . . 14 n, including volume group assignments 20 and alias addressdefinitions 22. The I/O manager code 12 buffers updates and requesteddata in the I/O cache 18 as the data is being transferred between thehosts 2 a, 2 b . . . 2 n and volumes 14 a, 14 b . . . 14 n.

The hosts 2 a, 2 b . . . 2 n may comprise computing systems capable ofcommunicating I/O requests over a network, such as a server,workstation, desktop, mainframe, laptop, hand held computing device,telephony device, etc. The control unit 6 may comprise a storage server,enterprise storage server, storage controller or other device used tomanage I/O requests directed to storage systems 4 managed by the controlunit. In one embodiment, the described operations to manage volumes areperformed on a zSeries® server host interconnections implemented in afiber connectivity (FICON) I/O interface. (FICON and zSeries areregistered trademarks of International Business Machines (IBM)Corporation) The storage system(s) 4 may include one or more storagedevices known in the art, such as interconnected hard disk drives (e.g.,configured as a DASD, RAID, JBOD, etc.), magnetic tape drive, electronicmemory, etc. The network 8 may comprise a local area network (LAN),storage area network (SAN), the Internet, and Intranet, a wirelessnetwork, bus interface, serial or parallel connection, etc.

FIG. 2 illustrates volume group information 50 included in the volumegroup assignment 20 for one volume group 50, including: a volume groupidentifier (ID) 52; an identifier of one or more hosts 54 assigned tothe volume group, such as a world wide node name or equivalentidentifier; one or more base addresses 56 assigned to the volume grouprepresenting volumes assigned to the volume group; and alias addresses58 assigned to the volume group 58, which may point to volume baseaddresses assigned to the volume group.

FIG. 3 illustrates alias address information 70 included in the aliasaddress definitions 22, including: an alias address 72; the underlyingbase address 74 to which the alias address points; and one volume group76 to which the alias address is assigned. Hosts assigned to the volumegroup to which an alias address is assigned may use the alias address todirect I/O requests to the volume base address to which the aliasaddress points. In this way, a host may concurrently submit and havepending multiple I/O requests to one volume using the volume baseaddress and the one or more alias addresses pointing to that volume baseaddress.

FIG. 4 illustrates operations performed by the I/O manager 12 toconfigure and manage volumes and volume groups. The I/O manager 12initiates (at block 100) the volume configuration and managementoperations in response to commands submitted by a user of the controlunit 6 or one host 2 a, 2 b . . . 2 n authorized to configure volumegroups via a command line interface or a graphical user interface (GUI).The I/O manager 12 creates (at block 102) one or more base volumes thathave a defined allocation of storage space on the control unit 6 andautomatically assigns any created base volumes to a predefined defaultvolume group that contains all base volumes. The I/O manager 12optionally assigns (at block 104) sets of volumes to volume groups byassigning volume base addresses to volume groups besides the defaultvolume group.

The I/O manager 12 may also generate (at block 106) at least one aliasaddress that is assigned to only one volume group and that points to adefined base address that is a base volume in the same volume groupincluding the generated alias address. Each host is assigned (at block108) a single volume group wherein the host 2 a, 2 b . . . 2 n only hasaccess to the base and alias volumes in its defined volume group. (Abase or alias volume not configured in the host's volume group appearsto be an unconfigured volume address to that host. A volume in more thanone volume group can be accessed by any hosts that have access to avolume group including the base address).

A host or the configuration process may redefine (at block 110) the baseaddress of an alias to point to a different base address that isconfigured within the alias address's assigned volume group. Inembodiments where a host only has access to a single volume group andthe aliases in that volume group can only be configured to base volumesconfigured to the volume group, the alias address cannot be used toaccess base volumes that are not assigned to the volume group. Thisconstraint supports aliases to be used to access base volumes in thevolume group that are dedicated (assigned to only this volume group) orshared (assigned to this volume group and other volume groups) withoutallowing them to access base volumes that are not configured to thehost's volume group. The I/O manager 12 assigns (or generates) (at block112) different alias addresses in the at least two volume groupsincluding the specified base address to point to the specified baseaddress. Further, the base addresses of all volumes configured in thestorage system, including all volumes assigned to volume groups, may beassigned (at block 114) to a default volume group enabling a third hostassigned to the default volume group to access all volumes. Inembodiments where there is a default volume group, the administrator orstorage resource provider may always keep a volume base address assignedto the default volume group, although volume base addresses may beremoved from a client volume group as part of the storage resourcemanagement.

In one embodiment, the assigned alias address may not be assigned to avolume base address in another volume group and hosts only use aliasaddresses assigned to the volume group to which the host is assigned.Alias address information 70 (FIG. 3) would be created for the generatedalias address identifying the alias address 72, the volume base address74 to which the alias address 72 points and the assigned volume group 76including the volume base address pointed to by the generated basealias. The I/O manager 12 may generate alias addresses when initiallyconfiguring a volume or in response to a request from a host 2 a, 2 b .. . 2 n for additional alias addresses. The hosts 2 a, 2 b . . . 2 n mayrequest reassignment of the base addresses of the aliases they canaccess if the size of their I/O queues for a volume or time I/O requestsremain queued exceeds certain performance thresholds.

Further, in the embodiment where the I/O manager 12 assigns (at block114) the base addresses of all volumes 14 a, 14 b . . . 14 n configuredin the storage system(s) 4 to a default volume group, a third oradditional host assigned to the default volume group may access allvolumes. Volumes assigned to the default volume group may be assigned toother volume groups to enable access to other hosts not assigned to thedefault volume group. In one embodiment, the hosts, such as first andsecond hosts, assigned to volume groups may be owned by separateorganizations, such as companies, user groups, individual users, etc.,that are clients of a storage resource provider, e.g., storage farm. Insuch case, the storage resource provider uses the host assigned to thedefault volume group to manage all volumes assigned to different clientvolume groups. This allows the storage resource provider to create,modify and delete volume groups and the volume base and alias addressesassigned to volume groups through managing the default volume group.

FIG. 5 illustrates operations performed by the I/O manager 12 to removeone specified base volume from one volume group. This request may bereceived by the administrator of the control unit 6 managing the volumegroups. Upon receiving (at block 150) a request to delete one specifiedvolume 14 a,14 b . . . 14 n identified by a base volume address from onespecified volume group, the I/O manager 12 performs (at block 152) oneof the following two operations with respect to any alias addresses inthe volume group that the base address is being removed from and thatpoints to the base volume to be removed: (1) reassign the alias addressto another base address in its associated volume group, if any (eitherautomatically or by prior configuration operation) or (2) delete thealias address (either automatically or by prior configurationoperation). The I/O manager 12 then removes (at block 154) the baseaddress from the specified volume group. The hosts assigned to thisvolume group lose access to the deleted base volume address.

FIG. 6 illustrates operations performed by the I/O manager 12 to deletean alias address. Upon receiving (at block 170) a request to delete analias address, the I/O manager 12 removes (at block 172) the aliasaddress from its associated volume group and the hosts assigned to thatvolume group lose access to the alias address. The alias address is thendeleted (at block 174).

FIG. 7 illustrates operations performed by the I/O manager 12 to deletea base volume. Upon receiving a request to delete (at block 180) a basevolume, with respect to any alias address (in any volume group that thebase volume is assigned to) that has the base volume to be deleted asits assigned base volume address, the I/O manager 12 performs (at block182) either (1) reassigning the alias address to another base address inits associated volume group, if any (either automatically or by priorconfiguration operation) or (2) deleting the alias address (eitherautomatically or by prior configuration operation). The base volume isremoved (at block 184) from all volume groups that it was configured toand the hosts assigned to those volume groups lose access to the basevolume address. The base volume is then deleted (at block 186).

ADDITIONAL EMBODIMENT DETAILS

The described embodiments may be implemented as a method, apparatus orarticle of manufacture using standard programming and/or engineeringtechniques to produce software, firmware, hardware, or any combinationthereof. The term “article of manufacture” as used herein refers to codeor logic implemented in hardware logic (e.g., an integrated circuitchip, Programmable Gate Array (PGA), Application Specific IntegratedCircuit (ASIC), etc.) or a computer readable medium, such as magneticstorage medium (e.g., hard disk drives, floppy disks,, tape, etc.),optical storage (CD-ROMs, optical disks, etc.), volatile andnon-volatile memory devices (e.g., EEPROMs, ROMs, PROMs, RAMs, DRAMs,SRAMs, firmware, programmable logic, etc.). Code in the computerreadable medium is accessed and executed by a processor. The code inwhich preferred embodiments are implemented may further be accessiblethrough a transmission media or from a file server over a network. Insuch cases, the article of manufacture in which the code is implementedmay comprise a transmission media, such as a network transmission line,wireless transmission media, signals propagating through space, radiowaves, infrared signals, etc. Thus, the “article of manufacture” maycomprise the medium in which the code is embodied. Additionally, the“article of manufacture” may comprise a combination of hardware andsoftware components in which the code is embodied, processed, andexecuted. Of course, those skilled in the art will recognize that manymodifications may be made to this configuration without departing fromthe scope of the present invention, and that the article of manufacturemay comprise any information bearing medium known in the art.

The reference letter “n” is used to refer to an instance number of anelement, e.g., hosts 2 a, 2 b . . . 2 n, volumes 14 a, 14 b . . . 14 n,and may indicate a different or same number of elements in differentusages. For instance the number of hosts 2 n may differ from the numberof volumes 14 n.

FIGS. 2 and 3 show certain information included in volume groupinformation and alias address information. In alternative embodiments,this information may be stored in different data structures havingdifferent formats and information than shown. For instance, there may bea separate data structure associating hosts with the volume groups towhich they are assigned.

Certain embodiments may be directed to a method for deploying computinginstruction by a person or automated processing integratingcomputer-readable code into a computing system, wherein the code incombination with the computing system is enabled to perform theoperations of the described embodiments.

The illustrated operations of FIGS. 4, 5, 6, and 7 show certain eventsoccurring in a certain order. In alternative embodiments, certainoperations may be performed in a different order, modified or removed.Moreover, steps may be added to the above described logic and stillconform to the described embodiments. Further, operations describedherein may occur sequentially or certain operations may be processed inparallel. Yet further, operations may be performed by a singleprocessing unit or by distributed processing units.

The foregoing description of various embodiments of the invention hasbeen presented for the purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseform disclosed. Many modifications and variations are possible in lightof the above teaching. It is intended that the scope of the invention belimited not by this detailed description, but rather by the claimsappended hereto. The above specification, examples and data provide acomplete description of the manufacture and use of the composition ofthe invention. Since many embodiments of the invention can be madewithout departing from the spirit and scope of the invention, theinvention resides in the claims hereinafter appended.

1. A method for providing hosts access to volumes configured in a storage system, comprising: assigning a first set of volumes to a first volume group; assigning a first host to the first volume group; assigning a second set of volumes to a second volume group; and assigning a second host to the second volume group, wherein the first host may only access volumes in the first volume group and the second host may only access volumes in the second-volume group, wherein one volume is assigned to both the first and second volume groups to be accessible to both the first and second hosts.
 2. The method of claim 1, wherein the host is identified such that the identification of the host is used to assign the host to one volume group in a volume group definition.
 3. The method of claim 1, wherein each volume has a base address, wherein the volume base addresses are assigned to the volume groups to which the volumes are assigned, further comprising: defining at least one alias address that points to one base address to enable one host to concurrently submit multiple Input/Output (I/O) requests to one volume using the base address and the at least one alias address pointing to that base address.
 4. The method of 3, further comprising: assigning each alias address to, the volume group including the base address to which the alias address points in response to generating the alias address, wherein the assigned alias address may not be assigned to a base address in another volume group, and wherein hosts only have access to the alias addresses to which the host is assigned.
 5. The method of claim 3, further comprising: assigning one specified base address for one volume to at least two volume groups; and assigning different alias addresses in the at least two volume groups including the specified base address to point to the specified base address, wherein the alias addresses are not assigned to base volumes outside of the volume group to which the alias is assigned.
 6. The method of claim 3, further comprising: modifying one alias address in a specified volume group to point to a different base address in the specified volume group, wherein the alias address assigned to one volume group cannot be modified to point to one base address in a different volume group.
 7. The method of claim 3, further comprising: receiving a request to delete one specified base volume from one specified volume group; modifying at least one alias address pointing to the specified base volume to delete so that there are no alias addresses in the specified volume group pointing to the specified base address to delete in response to receiving the request to delete the base volume; and deleting the base address from the specified volume grouping in response to modifying the at least one alias address.
 8. The method of claim 3, wherein modifying the at least one alias address comprises either reasssigning the alias address to another base address associated with the specified volume group or deleting the alias address.
 9. The method of claim 3, further comprising: assigning the base addresses of all volumes configured in the storage system, including volumes in the first and second sets, to a default volume group enabling a third host assigned to the default volume group to access all volumes, wherein volumes assigned to the default volume group are capable of being assigned to other volume groups to enable access to other hosts not assigned to the default volume group.
 10. The method of claim 9, wherein the first and second hosts are owned by separate organizations that are clients of a storage resource provider, wherein the storage resource provider uses the third host assigned to the default volume group to manage all volumes assigned to different client volume groups.
 11. The method of claim 3, further comprising: assigning multiple hosts to one specified volume group, wherein the hosts assigned to the specified volume group are enabled to share all base and alias addresses assigned to the specified volume group.
 12. The method of claim 3, further comprising: receiving a request to delete a specified alias address from a specified volume group; removing the specified alias address from the specified volume group to which the specified alias address is assigned, wherein hosts assigned to the specified volume group lose access to the alias address; and deleting the specified alias address in response to removing the specified alias address from the specified volume group.
 13. The method of claim 3, further comprising: receiving a request to delete a specified base volume; determining alias addresses in the volume group including the specified base volumes that point to the specified base volume; modifying each determined alias address to point to another base volume address in the volume group in which the determined alias address and specified base volume are included; and deleting the specified base volume in response to modifying the determined alias addresses.
 14. A system in connection with hosts and volumes configured in a storage system, comprising: a processor; and a computer readable medium including code executed by the processor to perform operations, the operations comprising: (i) assigning a first set of volumes to a first volume group; (ii) assigning a first host to the first volume group; (iii) assigning a second set of volumes to a second volume group; and (iv) assigning a second host to the second volume group, wherein the first host may only access volumes in the first volume group and the second host may only access volumes in the second volume group, wherein one volume is assigned to both the first and second volume groups to be accessible to both the first and second hosts.
 15. The system of claim 14, wherein the host is identified such that the identification of the host is used to assign the host to one volume group in a volume group definition.
 16. The system of claim 14, wherein each volume has a base address, wherein the volume base addresses are assigned to the volume groups to which the volumes are assigned, wherein the operations further comprise: defining at least one alias address that points to one base address to enable one host to concurrently submit multiple Input/Output (I/O) requests to one volume using the base address and the at least one alias address pointing to that base address.
 17. The system of claim 16, wherein the operations further comprise: assigning each alias address to the volume group including the base address to which the alias address points in response to generating the alias address, wherein the assigned alias address may not be assigned to a base address in another volume group, and wherein hosts only have access to the alias addresses to which the host is assigned.
 18. The system of claim 16, wherein the operations further comprise: assigning one specified base address for one volume to at least two volume groups; and assigning different alias addresses in the at least two volume groups including the specified base address to point to the specified base address, wherein the alias addresses are not assigned to base volumes outside of the volume group to which the alias is assigned.
 19. The system of claim 16, wherein the operations further comprise: modifying one alias address in a specified volume group to point to a different base address in the specified volume group, wherein the alias address assigned to one volume group cannot be modified to point to one base address in a different volume group.
 20. The system of claim 16, wherein the operations further comprise: receiving a request to delete one specified base volume from one specified volume group; modifying at least one alias address pointing to the specified base volume to delete so that there are no alias addresses in the specified volume group pointing to the specified base address to delete in response to receiving the request to delete the base volume; and deleting the base address from the specified volume grouping in response to modifying the at least one alias address.
 21. The system of claim 16, wherein modifying the at least one alias address comprises either reasssigning the alias address to another base address associated with the specified volume group or deleting the alias address.
 22. The system of claim 16, wherein the operations further comprise: assigning the base addresses of all volumes configured in the storage system, including volumes in the first and second sets, to a default volume group enabling a third host assigned to the default volume group to access all volumes, wherein volumes assigned to the default volume group are capable of being assigned to other volume groups to enable access to other hosts not assigned to the default volume group.
 23. The system of claim 22, wherein the first and second hosts are owned by separate organizations that are clients of a storage resource provider, wherein the storage resource provider uses the third host assigned to the default volume group to manage all volumes assigned to different client volume groups.
 24. The system of claim 16, wherein the operations further comprise: assigning multiple hosts to one specified volume group, wherein the hosts assigned to the specified volume group are enabled to share all base and alias addresses assigned to the specified volume group.
 25. The system of claim 16, wherein the operations further comprise: receiving a request to delete a specified alias address from a specified volume group; removing the specified alias address from the specified volume group to which the specified alias address is assigned, wherein hosts assigned to the specified volume group lose access to the alias address; and deleting the specified alias address in response to removing the specified alias address from the specified volume group.
 26. The system of claim 16, wherein the operations further comprise: receiving a request to delete a specified base volume; determining alias addresses in the volume group including the specified base volumes that point to the specified base volume; modifying each determined alias address to point to another base volume address in the volume group in which the determined alias address and specified base volume are included; and deleting the specified base volume in response to modifying the determined alias addresses.
 27. An article of manufacture for providing hosts access to volumes configured in a storage system, wherein the article of manufacture is enabled to perform operations, the operations comprising: assigning a first set of volumes to a first volume group; assigning a first host to the first volume group; assigning a second set of volumes to a second volume group; and assigning a second host to the second volume group, wherein the first host may only access volumes in the first volume group and the second host may only access volumes in the second volume group, wherein one volume is assigned to both the first and second volume groups to be accessible to both the first and second hosts.
 28. The article of manufacture of claim 27, wherein the host is identified such that the identification of the host is used to assign the host to one volume group in a volume group definition.
 29. The article of manufacture of claim 27, wherein each volume has a base address, wherein the volume base addresses are assigned to the volume groups to which the volumes are assigned, further comprising: defining at least one alias address that points to one base address to enable one host to concurrently submit multiple Input/Output (I/O) requests to one volume using the base address and the at least one alias address pointing to that base address.
 30. The article of manufacture of claim 29, wherein the operations further comprise: assigning each alias address to the volume group including the base address to which the alias address points in response to generating the alias address, wherein the assigned alias address may not be assigned to a base address in another volume group, and wherein hosts only have access to the alias addresses to which the host is assigned.
 31. The article of manufacture of claim 29, wherein the operations further comprise: assigning one specified base address for one volume to at least two volume groups; and assigning different alias addresses in the at least two volume groups including the specified base address to point to the specified base address, wherein the alias addresses are not assigned to base volumes outside of the volume group to which the alias is assigned.
 32. The article of manufacture of claim 29, wherein the operations further comprise: modifying one alias address in a specified volume group to point to a different base address in the specified volume group, wherein the alias address assigned to one volume group cannot be modified to point to one base address in a different volume group.
 33. The article of manufacture of claim 29, wherein the operations further comprise: receiving a request to delete one specified base volume from one specified volume group; modifying at least one alias address pointing to the specified base volume to delete so that there are no alias addresses in the specified volume group pointing to the specified base address to delete in response to receiving the request to delete the base volume; and deleting the base address from the specified volume grouping in response to modifying the at least one alias address.
 34. The article of manufacture of claim 29, wherein modifying the at least one alias address comprises either reasssigning the alias address to another base address associated with the specified volume group or deleting the alias address.
 35. The article of manufacture of claim 29, wherein the operations further comprise: assigning the base addresses of all volumes configured in the storage system, including volumes in the first and second sets, to a default volume group enabling a third host assigned to the default volume group to access all volumes, wherein volumes assigned to the default volume group are capable of being assigned to other volume groups to enable access to other hosts not assigned to the default volume group.
 36. The article of manufacture of claim 35, wherein the first and second hosts are owned by separate organizations that are clients of a storage resource provider, wherein the storage resource provider uses the third host assigned to the default volume group to manage all volumes assigned to different client volume groups.
 37. The article of manufacture of claim 29, wherein the operations further comprise: assigning multiple hosts to one specified volume group, wherein the hosts assigned to the specified volume group are enabled to share all base and alias addresses assigned to the specified volume group.
 38. The article of manufacture of claim 29, wherein the operations further comprise: receiving a request to delete a specified alias address from a specified volume group; removing the specified alias address from the specified volume group to which the specified alias address is assigned, wherein hosts assigned to the specified volume group lose access to the alias address; and deleting the specified alias address in response to removing the specified alias address from the specified volume group.
 39. The article of manufacture of claim 29, wherein the operations further comprise: receiving a request to delete a specified base volume; determining alias addresses in the volume group including the specified base volumes that point to the specified base volume; modifying each determined alias address to point to another base volume address in the volume group in which the determined alias address and specified base volume are included; and deleting the specified base volume in response to modifying the determined alias addresses.
 40. A method for deploying computing instructions, comprising integrating computer-readable code into a system accessible to volumes configured in a storage system, wherein the code is executed by the system to perform operations comprising: assigning a first set of volumes to a first volume group; assigning a first host to the first volume group; assigning a second set of volumes to a second volume group; and assigning a second host to the second volume group, wherein the first host may only access volumes in the first volume group and the second host may only access volumes in the second volume group, wherein one volume is assigned to both the first and second volume groups to be accessible to both the first and second hosts.
 41. The method of claim 40, wherein each volume has a base address, wherein the volume base addresses are assigned to the volume groups to which the volumes are assigned, further comprising: defining at least one alias address that points to one base address to enable one host to concurrently submit multiple Input/Output (I/O) requests to one volume using the base address and the at least one alias address pointing to that base address. 